MANILA, PHILIPPINES—A typhoon blew out of the northern Philippines on Wednesday after causing at least 20 deaths, knocking out power in entire provinces, damaging two parked jetliners and forcing nearly half a million people to flee from its lethal wind and rains, officials said.

The eye of Typhoon Rammasun made a late shift away from Manila, but its peak winds of 150 kilometres per hour and gusts up to 185 km/h forced down trees and electric posts and ripped off roofs across the capital of 12 million people that largely shut down ahead of the deluge.

Residents of the slum community of Baseco evacuate to safer ground during typhoon Rammasun in Manila on Wednesday.

Although Rammasun packed far less power than Typhoon Haiyan, haunting memories of last year's horrific storm devastation prompted many villagers to rapidly move to safety at the prodding of authorities. Of the half a million people affected by Rammasun, more than 423,000 fled to emergency shelters, according to the National Disaster Risk Reduction and Management Council.

In a shantytown at the edge of Manila Bay, hundreds of people fled when strong winds started to tear tin roofs off their shanties. Manila Mayor Joseph Estrada said his city staged anti-disaster drills two weeks ago precisely to prevent massive deaths during a catastrophe and he was relieved that only a few residents sustained injuries Wednesday.

While the low human toll has been attributed to the typhoon skipping Manila, Estrada believed the public's higher awareness of anti-disaster manoeuvrs saved many lives. He acknowledged that the wind and rain weren't as deadly as many have feared and it was a good time for everyone to hone their survival skills.

“It was like a drill,” Estrada told The Associated Press.

Officials reported at least 20 deaths elsewhere, mostly people pinned by falling trees and electrical posts. A fire volunteer died when he was hit by a block of concrete while hauling down a Philippine flag in suburban Pasig city, said Francis Tolentino, chairman of the Metropolitan Manila Development Authority.

Three fishermen were reported missing in Catanduanes, near Albay province, where Rammasun made landfall late Tuesday.

At Manila's international airport, the left wing of a Singapore Airlines Boeing 777 was damaged after strong gusts pushed it against a bridge passageway, manager Angel Honrado said. No one was injured.

One other parked jetliner reportedly sustained minor damages.

There were no immediate estimates of the damage in many communities that lost power and telephone connections.

Polangui Mayor Cherilie Mella Sampal said 10,000 of the 80,000 residents in her Albay town, about 340 kilometres southeast of Manila, abandoned their homes before the typhoon, many of them worried after witnessing Haiyan's deadly aftermath in the central Philippines last November.

At least 6,300 people died and more than 1,000 were left missing from Haiyan, one of the most ferocious typhoons to hit land.

“We're used to and prepared for calamities,” Sampal said. “But when people heard that the eye of the typhoon will hit the province, they feared we may end up like the victims” of Haiyan.

Although Rammasun slightly weakened as it scythed across the country's main northern region, it may strengthen over the South China Sea before slamming either Vietnam or southern China, according to government forecasters.

Rammasun, the Thai term for god of thunder, is the seventh storm to batter the Philippines this year. About 20 typhoons and storms lash the archipelago on the western edge of the Pacific each year, making it one of the world's most disaster-prone countries.